Wireless power transfer (WPT) is the transmission of energy or power from a source to a load without a wire. WPT can be used in a wide variety of applications, for example, to directly power electronic devices and/or recharge batteries. A conventional inductive or resonant inductive WPT system normally includes a transmitter (Tx) side circuit, a Tx coil, a receiver (Rx) coil, and Rx side electronics/load. The major part of the Tx side circuit is the DC-AC inverter/power amplifier such as full-bridge/half-bridge inverter and class-E power amplifier. The generated high frequency AC drives the Tx coil to create oscillating magnetic field in the proximity of the Tx coil. Energy is then delivered to Rx coil through this oscillating magnetic field to realize WPT. The Tx side circuitry and Tx coil are essential parts in conventional WPT system but they are bulky in size and weight.
On the other hand, wired power transmission and regulation can be done using power regulation circuits such as DC-DC, AC-DC, and DC-AC power converters and inverters. Switching power converters and inverters usually include one or more power inductors. Taking a switching DC-DC power converters as an example, its power inductor carries a desired DC current to deliver energy to the load but also there is a natural oscillating current AC ripple component imposed on the DC current component. The current AC ripple components is usually undesired and design goal is to reduce it. This AC ripple current component causes additional loss in the power converter and result in electromagnetic interference.
The use of this current AC ripple component has not been explored and is also considered a disadvantage. As described above, state-of-the-art circuits and controllers used for wireless power transmission are different from the state-of-the-art circuits and controllers used for wired power transmission.